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Zeolite nanopore model links crystal size to metal cluster migration and catalyst performance

Extensive industrial catalytic applications have shown that the confined nano-channels of zeolites can precisely regulate molecular diffusion and metal cluster migration, effectively enhancing catalyst activity, selectivity, and stability.

A deep understanding and quantitative description of the coupling between confined "transport and reaction" processes are essential for designing and optimizing industrial zeolite catalysts. However, constructing such a theoretical model poses a significant challenge, largely due to the difficulty in precisely characterizing and describing these confined transport phenomena.

To address this challenge, a research team, led by Prof. Liu Zhongmin and Prof. Ye Mao from the Dalian Institute of Chemical ��������ics (DICP) of the Chinese Academy of Sciences (CAS), in collaboration with Prof. Bao Xiaojun and Prof. Zhu Haibo from Fuzhou University, has proposed a theoretical model describing the migration-aggregation behavior of confined metal clusters within individual zeolites.

The study is in Nature.

Using advanced first-principles simulations, the researchers investigated the migration and aggregation kinetics of metal clusters within the nanopores of silicate-1 (S-1). This work led to the establishment—for the first time—of a theoretical model specifically describing the migration-aggregation process of metal clusters within zeolite nanopores.

This model reveals the dynamic behavior of metal clusters within the S-1 micro-region and quantitatively describes how the crystal size of S-1 affects the spatial and temporal distribution of these clusters. The model's reliability was validated through various in-situ high-spatial-resolution spectroscopic characterizations.

Using this model, researchers discovered that the crystal size of S-1 plays a key role in regulating two competing mechanisms: surface aggregation of metal clusters, which leads to the formation of low-activity metal nanoparticles, and aggregation within the nanopores, which results in high-activity sub-nanometer metal clusters.

Furthermore, the researchers found that when the b-axis length of S-1 exceeds 2 μm, the extended migration path drives Pt species to aggregate within the pores, forming sub-nanometer Pt clusters. These clusters become effectively locked in place within the nanopores, thereby preventing irreversible catalyst deactivation.

Based on this mechanism, the researchers proposed a strategy to achieve the "migration-aggregation-self-locking" of Pt species by increasing the crystal size of S-1. This approach enabled the creation of an ultra-stable Pt-Sn@MFI catalyst for propane dehydrogenation.

"Our study quantitatively describes metal cluster migration and aggregation within individual zeolites, offering an important theoretical foundation for precisely regulating confined metal cluster migration-aggregation by adjusting zeolite support properties," said Prof. Ye.